MONITORING AND FORECAST

JAPAN,  Мs≥7.8

Seismic danger in Tokyo area, after the refinement of the magnitude of earthquake dated July 19, 2008, decreased  /31 July 2008/.

Situation in the system.

In the communication dated July 10, 2008, we noted that if occurs the earthquake-indicator with the magnitude Ms equal to 7.0, then danger will move from the area of Tokyo to the north. In the communication dated July 20, 2008 we noted that there are some divergences in the determination of the magnitude Ms of earthquake July 19, 2008. Then, for the calculations we accepted the magnitude of this earthquake of Ms=6.8 as most unfavorable for Tokyo. Since the value of the magnitude of this earthquake is very important for the rescuing by Tokyo, we analyze the prevailing situation. It is clear, that than greater the magnitude, the greater the chance, that the track of the preparation of strong earthquake will on top go around unstable regions for Tokyo area on the track diagram (for zones A,B,C to Fig.1).

At present, on July 31, 2008, after refinement by the U.S. Geological Survey (USGS) the magnitude of earthquake dated July 19, 2008 of Ms=7.0 off the East coast of Honshu☼, we produced the overestimation of seismic situation in Tokyo area. The results of update are given in Tab.1 and on Fig.2.

The value of cumulative energy for the unstable region of historical earthquake to 1703 Genroku (zone C) is unknown. For this earthquake, on the basis of our experience, as upper value we accepted the value of cumulative energy of the earthquake of Boso Oki (K=16.764). Because of the uncertainty of catalogs before 1960 (because of the passages relative to weak seismicity) in our estimations this value it is possible to increase maximum by 0.15% which composes K=16.789 (see Tab.1). As we see from Tab.1, now after the overestimation of the magnitude of earthquake dated July 19, 2008, the parameter K=16.793 (earlier it was 16.780). I.e., it is purely quantitative, from the parameter of cumulative energy, because of two earthquakes dated June 13 and July 19, 2008 (see Fig.1) track jumped upward and it left the unstable region of zones A,B,C. It moves hope, that the danger of strong earthquake from Ms> 7.8 for Tokyo considerably it decreased.

Finally it is possible to be quieted only after August, since by the entropy during August the trajectory will be located in the unstable region of zones A,B,C (see Fig.1 and Tab.1). With the corrections given above, the reasonings, given in the communication dated July 20, 2008 remain valid

Probability of strong earthquake from Ms>7.8 in the seismic system Japan in August equal to P=41% (on entropy P_W=61%, and on cumulative energy P_K=67%) (see Fig.2 and Tab.1).

Fig.1. Japan. Controlled region of the forecast of earthquakes from M≥7.8. Seismic danger in Tokyo region considerably decreased after the refinement of the magnitude of earthquake dated July 19, 2008, M=7.0. The source of the expected strong earthquake on the entropy in August will be thus far localized in central Japan, in the zone C, but it has a tendency of migration toward the north to the zone D.

Fig.2. Dynamics of an increase in the probability of strong earthquake in SS Japan in August 2008, after the refinement of the magnitude of earthquake from 19.07.08

Table 1. Increase in the dynamic parameters of the preparation of strong earthquake (Ms≥7.8) in SS Japan in July - August 2008, after earthquake dated July 19, 2008 from Ms=7.0 and the nearest zones of instability. Danger on the entropy remains.

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